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Wiring/testing motor for Hobart AM-14 commercial dishwasher

Wiring/testing motor for Hobart AM-14 commercial dishwasher

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  #1  
Old 05-26-18, 09:19 PM
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Wiring/testing motor for Hobart AM-14 commercial dishwasher

Hello,
I have been working on repairing a Hobart AM-14 commercial dishwasher. I believe that the motor is burned out, but I would like to verify this before proceeding. I have disconnected the motor from the machine both physically and electrically. I would now like to test functionality with a multimeter and/or by wiring to a AC plug. I need some help with testing and wiring. Here is a description of the electrical. The motor has 8 wires coming out of it; four heavier gauge and four lighter gauge. The wires go into a terminal block that seems to be able to switch between high and low voltage. Here is a link to some pictures for reference:
https://photos.app.goo.gl/dsQ4t7c2EDvgjfQs1
Thanks,
icecats
 
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Old 05-27-18, 10:27 AM
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Line wires should go on L1 and L2. L3 would be for a three phase motor, but the nameplate says single phase so that shouldn't be used.

To test the motor you can try to read through the windings of the motor using a meter.
You could also just apply voltage to it and see if it spins.
 
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Old 05-27-18, 11:28 AM
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You could also just apply voltage to it and see if it spins.
To do this, would I connect hot and neutral wires from 120 VAC source to the the L1 and L2 (does it matter which is connected to which)? I would also need to move the cover plate of the terminals to LOW setting to correspond to lower voltage. Does this sound correct?
Thanks
 
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Old 05-27-18, 12:00 PM
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It does not matter which wire goes where, it is alternating current.

Yes, set the motor to the low voltage setting if connecting to 120 volts
 
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Old 05-27-18, 02:34 PM
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Ok- I hooked up the wires and plugged everything in. The motor hummed and spun briefly and then the breaker tripped. Any ideas?
Thanks
 
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Old 05-27-18, 04:48 PM
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What size wire/circuit breaker are you trying to run it on? Nameplate says it draws 15.6 @ 120 volts. A motor can draw three times that during startup.
 
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Old 05-27-18, 06:47 PM
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I was originally using 18 awg on a 20 amp breaker which was obviously wrong.
I switched to a 220v, 50 amp circuit. The motor does not move or make any noise whatsoever. Perhaps this means that it is fried? The only thing that bothers me about this is that I did see some movement and noise on the 120v circuit.
A somewhat separate question. Do you know the purpose of the other 4, smaller gauge wires?
Thanks
 
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Old 05-27-18, 07:53 PM
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If the motor was wired for 120v..... you can not apply 240v to it without rewiring. That motor has a centrifugal start switch and a capacitor in it. The cap and start switch are probably the smaller wires.

You need to know for sure what voltage the appliance was running on.
 
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Old 05-27-18, 08:45 PM
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The cover on the terminal block can be removed and shifted to switch between high and low voltage- at least, I think that is the intended purpose. The second picture here shows this.
 
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Old 05-28-18, 06:51 AM
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Try it again on a 120 volt circuit using #12 wires and a 20 amp circuit switching the block around for low voltage. I also suspect the motor is shot, but one more test will confirm.
 
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Old 05-28-18, 09:28 AM
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Indeed the motor must be dead. Out of curiosity, I disassembled it to have a look. Part of the coils are blackened, and the resistance of the coil is huge. I also noticed that the rotor has some wear marks on it; it seems like it was rubbing on the stator.
I am now looking for a replacement motor. 3450 RPM, single phase motors are very common and cheap. Before I purchase one, I want to make sure that I can figure out how to wire it up. The only thing that bothers me are those four smaller gauge wires. They connect straight to four wires coming from the dishwasher controller. I also don't think that they are part of the capacitor circuit (when looking inside, the small wires disappear into the coil). As far as I can tell, none of the replacement motors have these wires coming from them. For example, here is a motor I was looking at.
Thanks
 
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Old 05-28-18, 10:30 AM
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The cap and the start switch are inside the motor. If those four wires are brought out of the motor then I'm thinking one pair could be a heat sensor and the other pair could be for speed sensing to determine load.

It's going to be difficult to swap in a generic motor there. That should have a custom flange on it as well as some type of volute seal and impeller seal.

I've been looking for a "free" wiring diagram but they aren't free. Since you are servicing that unit you need to get a wiring diagram for it.
 
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Old 05-28-18, 10:14 PM
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120v motor in 240v circuit

Hello,
I am replacing the motor on a commercial Hobart dishwasher (see previous thread here). I have a motor from a broken air compressor that has all of the correct specs except it is a 120v motor. The dishwasher runs on a 240v circuit. I would like to wire the motor to a 120v outlet, but still have it be controlled by the 240v dishwasher. It seems like this is possible, but I am not sure how to wire everything up. The schematic for the dishwasher can be viewed here.
Thanks
 
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Old 05-28-18, 11:40 PM
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Threads combined.

An air compressor motor is a full air-over motor. It may not be up to the duty here. The control circuit/contactor delivers 240v volt. Without rewiring the machine you can't use a 120v motor. I don't think a 120v motor will have the power to operate the wash pump properly.

The extra four small wires are for thermal sensors that are in the motor.
The controller may not operate without them.

Are you fixing this for your own use or to sell ?
Tough to sell without it operating as a Hobart machine should.
 
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Old 05-29-18, 09:23 AM
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I am fixing the dishwasher for a non-profit I volunteer at. The stakes are not super high- I either fix the machine or we continue to have an unusable dishwasher.
 
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